This invention relates to chains, and more particularly, to chains which include carrier rollers for supporting the weight of articles conveyed by the chain.
The use of resilient roller tires in carrier rollers which travel over rails has been found to be preferable to metal rollers in many cases, because a resilient roller tire does less damage to the track and because a track is less likely to cut or scratch and thereby damage a resilient roller tire. There are, however, several problems which are encountered with resilient roller tires.
First, if intermittent large overloads are placed on resilient roller tires, due to something other than the articles conveyed by the chain such as, for example, trucks being driven across the conveyor, the resilient roller tires, and the bearings on which they are mounted, tend to fail under the excess load. The problem of intermittent excess loads has been solved in cargo rollers to some extent by the roller shown in U.S. Pat. No. 4,203,509 which is hereby incorporated by reference and referred to as "Thompson".
The Thompson roller has a resilient tire mounted on a tubular body having radial flanges at both ends, the central part of the tire bulging so that it has a larger diameter than the diameter of the flanges. When a large load is placed on the tire, the tire deforms until the load is sustained directly via the radial flanges. This is a fairly complicated construction, and the load sustained by the flanges is also sustained by the bearing, so the bearing receives no greater protection with the flanges than it would without them. Furthermore, it is impossible to replace a damaged flange without replacing the entire cargo roller. The present invention provides a carrier roller in which the resilient roller tire and the bearing in the resilient roller tire have improved protection against overload.
A second problem encountered in resilient roller tires having integral flanges is that the flange tends to flex relative to the tire tread, resulting in fatigue failure. The present invention solves or minimizes this problem by restricting flexure of the flange.
A third problem encountered in these conveyors involves the lack of support for the top plates which carry the articles being conveyed. In the prior art, such as shown in U.S. Pat. No. 3,842,970 "Brenner", which is hereby incorporated by reference, the rear portion of the top plate is supported by and welded to a pair of frame members on one chart carrier, and the front portion of the top plate is generally supported by the trailing portion of the preceding cart carrier. The contact with the preceding cart carrier is in a very narrow area along the frame members or landing pads of the leading cart carrier and does not provide enough support for extremely heavy loads. Furthermore, the top plates tend to misalign upon turning a corner or articulating over a sprocket and fail to properly realign, so that a smooth conveying surface is not provided for the articles being conveyed. The present invention provides more support for the top plates and provides guidance so that the plates tend to remain aligned during straight and laterally curving runs and to rapidly realign after passing over a sprocket.